.avatar{
    position:relative;
    width:100%;
    height:100%;
}

.avatar:after{
    position:absolute;
    width:100%;
    height:100%;
    content:"";
    display:block;
    top:0;
    left:0;
    background:url('/test/jzsb.jpg');
    filter:alpha(opacity=0);
    -moz-opacity:0;
    opacity:0;
    background-size:100%;}

.avatar:after{
    content: attr(alt);
}
.avatar img{
    width: 100%;
    height: 100%;
}